1. Field of the Invention
The invention relates to a photosensitive resin composition, an overcoat or a spacer formed by the composition and a liquid crystal display component. Particularly, the invention provides n overcoat or a spacer formed by the composition and a liquid crystal display component having good resolution and good developability manufactured with the photosensitive resin composition.
2. Description of the Related Art
Generally, color printed pixels and black matrix on a color filter produce an uneven surface. An overcoat is usually formed on the surface of the color filter to hide the uneven surface and to meet the requirement of flatness.
Demanding procedures under harsh conditions are required for manufacturing a liquid crystal display component or a solid-state imaging device, etc. For example, local high temperature occurs when processing by infusion with an acid solvent or alkaline solvent on the surface of substrate or by sputtering to form a wiring electrode layer. Thus, an overcoat is needed to be laid on these components to prevent them from damage. To enable the overcoat to resist the aforementioned processing, an excellent adhesive force between the overcoat and substrate is required, along with a surface of high transparency, high hardness and smoothness; furthermore, high heat resistance and light resistance could prevent the overcoat from deteriorations including: discoloration, yellowing or whitening, etc. Moreover, good water-proofing and strong resistance to chemicals, solvents, acid and alkali, etc, of the overcoat is also required.
On the other hand, to maintain an interlayer spacing (intercellular space) between two substrates in conventional colored liquid crystal display components, polystyrene beads or silica beads are randomly sprayed on the entire substrate, of which the diameter of the beads is the spacing between two substrates. However, uneven positioning and density distribution of the beads causes scattering of the backlight and further reducing the contrast of the display components. Therefore, a photosensitive composition for the spacer developed by photolithography becomes the mainstream in this field. The spacer is formed by coating the photosensitive composition for a spacer on the substrate, and placing a designated-shaped photomask between the substrate and the exposure source; then by development after exposure, a spacer is formed on a designated position outside the effective pixel to solve the problems in the prior art. The intercellular space is also controlled by the cell thickness formed by the photosensitive composition, enabling to control its spacing with high accuracy.
Nowadays, the overcoat and spacer are generally made of photosensitive resin by means of coating, exposure and developing, etc.
As the overcoat or spacer is formed on a colored filter or substrate, an extremely high transparency is required. When the overcoat or spacer with poor transparency is applied to a liquid crystal display component, inadequate luminance of the liquid crystal display component is caused, thus affecting its display quality.
To improve the transparency of the overcoat or spacer, Japanese Patent Publication No. 2010-054561 disclosed a photosensitive composition for an overcoat, comprising: an alkali-soluble bonding resin (A); an ethylenically unsaturated compound (B); a light initiator (C); and a solvent (D); wherein the bonding equivalent of the unsaturated bond in the ethylenically unsaturated compound (B) is between 90 and 450 g/eq, and the amount of unsaturated double bond of a single compound is between 2 and 4 in the ethylenically unsaturated compound (B); and the average molecular weight of the alkali-soluble bonding resin (A) is between 10,000 and 20,000. Additionally, Japanese Patent Publication No. 2004-240241 has disclosed a photosensitive composition comprising: a copolymer (A), which is polymerized by an ethylenically unsaturated carboxyl(anhydride), an ethylenically unsaturated compound containing an epoxy group and other unsaturated ethenyl compounds; an ethylenically unsaturated ethenyl polymer (B); and a photoinitiator (C). The photoinitiator (C) is 2-butanedione-[-4-methylthio benzene]-2-(O-oxime acetate), 1,2-butanedione-1-(-4-morpholino phenyl)-2-(O-benzoyl oxime), 1,2-octadione-1-[4-thiophenyl benzene]-2-[O-(4-methyl benzoyl)oxime] or its analogue. Though the photosensitive composition is able to fabricate an overcoat or spacer of high transparency, it presents poor resolution and developability.
Therefore, a photosensitive that enhancing the resolution and developability of the overcoat and spacer at the same time is a target remained to be achieved for the cost concern.